Pigment aggregation in shrimp chromatophores is triggered by red pigment concentrating hormone (RPCH), a neurosecretory peptide whose plasma membrane receptor may be a G-protein coupled receptor (GPCR). While RPCH binding activates the Ca2+/cGMP signaling cascades, a role for cyclic AMP (cAMP) in pigment aggregation is obscure, as are the steps governing Ca2+ release from the smooth endoplasmic reticulum (SER). A role for the antagonistic neuropeptide, pigment dispersing homone (α-PDH) is also unclear. In red, ovarian chromatophores from the freshwater shrimp Macrobrachium olfersi, we show that a G-protein antagonist (AntPG) strongly inhibits RPCH-triggered pigment aggregation, suggesting that RPCH binds to a GPCR, activating an inhibitory G-protein. Decreasing cAMP levels may cue pigment aggregation, since cytosolic cAMP titers, when augmented by cholera toxin, forskolin or vinpocentine, completely or partially impair pigment aggregation. Triggering opposing Ca2+/cGMP and cAMP cascades by simultaneous perfusion with lipid-soluble cyclic nucleotide analogs induces a “tug-of-war” response, pigments aggregating in some chromatosomes with unpredictable, oscillatory movements in others. Inhibition of cAMP-dependent protein kinase accelerates aggregation and reduces dispersion velocities, suggesting a role in phosphorylation events, possibly regulating SER Ca2+ release and pigment aggregation. The second messengers IP3 and cADPR do not stimulate SER Ca2+ release. α-PDH does not sustain pigment dispersion, suggesting that pigment translocation in caridean chromatophores may be regulated solely by RPCH, since PDH is not required. We propose a working hypothesis to further unravel key steps in the mechanisms of pigment translocation within crustacean chromatophores that have remained obscure for nearly a century.

The responses of estuarine invertebrates to hypoxic conditions are well established. However, many studies have investigated hypoxia as an isolated condition despite its frequent co-occurrence with hypercapnia (elevated CO2). Although many studies suggest deleterious effects, hypercapnia has been observed to improve blue crab walking performance in hypoxia. To investigate the physiological effects of combined hypercapnic hypoxia, we measured Po2, pH, [l-lactate], Pco2, and total O2 in pre- and postbranchial hemolymph sampled from blue crabs during walking exercise. Crabs walked at 8 m min−1 on an aquatic treadmill in normoxic (100% air saturation), moderately hypoxic (50%), and severely hypoxic (20%) seawater with and without the addition of hypercapnia (about 2% CO2). Respiration was almost completely aerobic in normoxic conditions, with little buildup of lactate. During exercise under severe hypoxia, lactate increased from 1.4 to 11.0 mM, indicating a heavy reliance on anaerobic respiration. The O2 saturation of arterial hemocyanin was 47% in severe hypoxia after 120 min, significantly lower than in normoxia (80%). However, the addition of hypercapnia significantly increased the percentage saturation of arterial hemocyanin in severe hypoxia to 92% after 120 min of exercise, equivalent to normoxic levels. Hypercapnia in severe hypoxia also caused a marked increase in hemolymph Pco2 (around 1.1 kPa), but caused only a minor decrease in pH of 0.1 units. We suggest that the improved O2 saturation at the gills results from a specific effect of molecular CO2 on hemocyanin oxygen binding affinity, which works independently of and counter to the effects of decreased pH.

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The responses of estuarine invertebrates to hypoxic conditions are well established. However, many studies have investigated hypoxia as an isolated condition despite its frequent co-occurrence with hypercapnia (elevated CO2). Although many studies suggest deleterious effects, hypercapnia has been observed to improve blue crab walking performance in hypoxia. To investigate the physiological effects of combined hypercapnic hypoxia, we measured Po2, pH, [l-lactate], Pco2, and total O2 in pre- and postbranchial hemolymph sampled from blue crabs during walking exercise. Crabs walked at 8 m min−1 on an aquatic treadmill in normoxic (100% air saturation), moderately hypoxic (50%), and severely hypoxic (20%) seawater with and without the addition of hypercapnia (about 2% CO2). Respiration was almost completely aerobic in normoxic conditions, with little buildup of lactate. During exercise under severe hypoxia, lactate increased from 1.4 to 11.0 mM, indicating a heavy reliance on anaerobic respiration. The O2 saturation of arterial hemocyanin was 47% in severe hypoxia after 120 min, significantly lower than in normoxia (80%). However, the addition of hypercapnia significantly increased the percentage saturation of arterial hemocyanin in severe hypoxia to 92% after 120 min of exercise, equivalent to normoxic levels. Hypercapnia in severe hypoxia also caused a marked increase in hemolymph Pco2 (around 1.1 kPa), but caused only a minor decrease in pH of 0.1 units. We suggest that the improved O2 saturation at the gills results from a specific effect of molecular CO2 on hemocyanin oxygen binding affinity, which works independently of and counter to the effects of decreased pH.
RESEARCH ARTICLE: Elevated environmental Pco2 improves arterial O2 saturation in blue crabs walking in severe hypoxia, enhancing oxygen delivery. This likely results from a specific effect of molecular CO2 that increases the O2 binding affinity of blue crab hemocyanin.
Female White-Footed Mice (Peromyscus leucopus) Trade Off Offspring Skeletal Quality for Self-Maintenance When Dietary Calcium Intake is Lowhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2051Female White-Footed Mice (Peromyscus leucopus) Trade Off Offspring Skeletal Quality for Self-Maintenance When Dietary Calcium Intake is LowCHRISTINA M. SCHMIDT, WENDY R. HOOD2016-11-30T05:06:00.481107-05:00doi:10.1002/jez.2051John Wiley & Sons, Inc.10.1002/jez.2051http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2051Research Articlen/an/aABSTRACT

During gestation and lactation in mammals, calcium and other minerals are transferred from female to offspring to support skeletal ossification. To meet mineral requirements, females commonly mobilize mineral from their own skeleton to augment dietary intake. Because the fitness costs of bone loss are expected to limit the amount of endogenous mineral that females transfer to their young, the amount of mineral allocated to offspring is predicted to be influenced by the availability of mineral in the female's diet. Calcium is the most abundant element in bone, and exogenous calcium appears to be limiting for many species. Thus, we expected that females would adjust mineral allocation to offspring relative to calcium abundance in the diet. We provided breeding female white-footed mice (Peromyscus leucopus) with a low-calcium (0.1% Ca) or a standard diet (0.85% Ca) for approximately 1 year. Body mass and skeletal size of pups did not differ between diets. Relative to pups from females on the standard diet, pups from females on the low-calcium diet had less calcium and phosphorus in their femurs and humeri, less body calcium content, reduced mass of their femurs and humeri, and had femurs with a reduced width. Reproducing white-footed mice mobilize more bone when calcium intake is low; however, our results suggest that this does not completely compensate for a reduction in calcium intake. Thus, it appears that when calcium availability is low, female white-footed mice reduce the quantity of mineral allocated per offspring as a means of maintaining their own skeletal condition.

Research Highlights

When calcium availability is low, reproducing female mice elevate bone mineral mobilization but also reduce the amount of mineral allocated to offspring. This suggests that there is a limit to the degree to which bone can be mobilized or reallocated.

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During gestation and lactation in mammals, calcium and other minerals are transferred from female to offspring to support skeletal ossification. To meet mineral requirements, females commonly mobilize mineral from their own skeleton to augment dietary intake. Because the fitness costs of bone loss are expected to limit the amount of endogenous mineral that females transfer to their young, the amount of mineral allocated to offspring is predicted to be influenced by the availability of mineral in the female's diet. Calcium is the most abundant element in bone, and exogenous calcium appears to be limiting for many species. Thus, we expected that females would adjust mineral allocation to offspring relative to calcium abundance in the diet. We provided breeding female white-footed mice (Peromyscus leucopus) with a low-calcium (0.1% Ca) or a standard diet (0.85% Ca) for approximately 1 year. Body mass and skeletal size of pups did not differ between diets. Relative to pups from females on the standard diet, pups from females on the low-calcium diet had less calcium and phosphorus in their femurs and humeri, less body calcium content, reduced mass of their femurs and humeri, and had femurs with a reduced width. Reproducing white-footed mice mobilize more bone when calcium intake is low; however, our results suggest that this does not completely compensate for a reduction in calcium intake. Thus, it appears that when calcium availability is low, female white-footed mice reduce the quantity of mineral allocated per offspring as a means of maintaining their own skeletal condition.
When calcium availability is low, reproducing female mice elevate bone mineral mobilization but also reduce the amount of mineral allocated to offspring. This suggests that there is a limit to the degree to which bone can be mobilized or reallocated.
Issue Informationhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.1983Issue Information2016-10-27T04:26:47.362828-05:00doi:10.1002/jez.1983John Wiley & Sons, Inc.10.1002/jez.1983http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.1983Issue Information479480Nutrient Stress During Ontogeny Alters Patterns of Resource Allocation in two Species of Horned Beetleshttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2050Nutrient Stress During Ontogeny Alters Patterns of Resource Allocation in two Species of Horned BeetlesDaniel B. Schwab, Armin P. Moczek2016-10-21T02:25:31.429755-05:00doi:10.1002/jez.2050John Wiley & Sons, Inc.10.1002/jez.2050http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2050Research Article481490ABSTRACT

The elaboration of exaggerated, sexually selected weapons and ornaments often comes at a cost to other traits. For instance, by sustaining the growth of an exaggerated weapon during development, shared and limited resources such as morphogens, growth factors, and nutrients may become depleted and limit the size to which other structures can grow. Such interactions are characteristic of resource allocation trade-offs, which can constrain the production of phenotypic variation and bias evolutionary trajectories. Across many species of Onthophagus beetles, males produce extravagant horns that are used as weapons in male–male competition over mates. Previous studies have reported resource allocation trade-offs between horns and both proximally and distally developing structures. However, more recent studies have largely failed to recover these patterns, leading to the hypothesis that trade-offs may manifest only in certain species, populations, or environmental conditions. Here, we investigate (i) patterns of resource allocation into horns, eyes, and genitalia in Onthophagus gazella and O. taurus, and assess (ii) how these patterns of resource allocation are influenced by nutrient stress during larval development. We find that nutrient stress alters patterns of resource allocation within and among traits, but recover a trade-off only in the species that invests most heavily into horn production (O. taurus), and in individuals of that species that invested a disproportionately large or small amount of resources into horn growth. These results suggest that resource allocation trade-offs may not be as prevalent as previously described, and that their presence and magnitude may instead be highly context dependent.

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The elaboration of exaggerated, sexually selected weapons and ornaments often comes at a cost to other traits. For instance, by sustaining the growth of an exaggerated weapon during development, shared and limited resources such as morphogens, growth factors, and nutrients may become depleted and limit the size to which other structures can grow. Such interactions are characteristic of resource allocation trade-offs, which can constrain the production of phenotypic variation and bias evolutionary trajectories. Across many species of Onthophagus beetles, males produce extravagant horns that are used as weapons in male–male competition over mates. Previous studies have reported resource allocation trade-offs between horns and both proximally and distally developing structures. However, more recent studies have largely failed to recover these patterns, leading to the hypothesis that trade-offs may manifest only in certain species, populations, or environmental conditions. Here, we investigate (i) patterns of resource allocation into horns, eyes, and genitalia in Onthophagus gazella and O. taurus, and assess (ii) how these patterns of resource allocation are influenced by nutrient stress during larval development. We find that nutrient stress alters patterns of resource allocation within and among traits, but recover a trade-off only in the species that invests most heavily into horn production (O. taurus), and in individuals of that species that invested a disproportionately large or small amount of resources into horn growth. These results suggest that resource allocation trade-offs may not be as prevalent as previously described, and that their presence and magnitude may instead be highly context dependent.
Populations of the Lizard, Sceloporus occidentalis, that Differ in Melanization have Different Rates of Wound Healinghttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2033Populations of the Lizard, Sceloporus occidentalis, that Differ in Melanization have Different Rates of Wound HealingRyan J. Seddon, Diana K. Hews2016-09-06T02:10:52.461566-05:00doi:10.1002/jez.2033John Wiley & Sons, Inc.10.1002/jez.2033http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2033Research Article491500ABSTRACT

Mechanisms underlying production of animal coloration can affect key traits besides coloration. Melanin, and molecules regulating melanin, can directly and indirectly affect other phenotypic traits, such as immune function. We asked whether melanization and a whole-organism measure of immune function are associated with wound healing. Working with two populations of adult male western fence lizards, Sceloporus occidentalis, we compared one high-elevation and one low-elevation population in California where individuals are increasingly darker at higher elevations, measuring wound healing rates. Because of potential interactions of steroid hormones and immune function, we also measured plasma levels of testosterone and corticosterone. Mean healing rates differed significantly, with males in the darker high-elevation population healing more quickly compared to lighter low-elevation males. Males in the low-elevation population had significantly higher mean baseline steroid concentrations. These steroid hormones were also negatively associated with wound healing. We discuss potential differences in selective regime that could produce different patterns. These data also suggest that hormonal pleiotropy does not constrain phenotypic variation.

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Mechanisms underlying production of animal coloration can affect key traits besides coloration. Melanin, and molecules regulating melanin, can directly and indirectly affect other phenotypic traits, such as immune function. We asked whether melanization and a whole-organism measure of immune function are associated with wound healing. Working with two populations of adult male western fence lizards, Sceloporus occidentalis, we compared one high-elevation and one low-elevation population in California where individuals are increasingly darker at higher elevations, measuring wound healing rates. Because of potential interactions of steroid hormones and immune function, we also measured plasma levels of testosterone and corticosterone. Mean healing rates differed significantly, with males in the darker high-elevation population healing more quickly compared to lighter low-elevation males. Males in the low-elevation population had significantly higher mean baseline steroid concentrations. These steroid hormones were also negatively associated with wound healing. We discuss potential differences in selective regime that could produce different patterns. These data also suggest that hormonal pleiotropy does not constrain phenotypic variation.
Testosterone and Haemosporidian Parasites Along a Tropical Elevational Gradient in Rufous-Collared Sparrows (Zonotrichia capensis)http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2034Testosterone and Haemosporidian Parasites Along a Tropical Elevational Gradient in Rufous-Collared Sparrows (Zonotrichia capensis)Camilo Escallón, Nicole M. Weinstein, James A. Tallant, Winfried Wojtenek, Carlos A. Rodríguez-Saltos, Elisa Bonaccorso, Ignacio T. Moore2016-08-16T00:45:26.779205-05:00doi:10.1002/jez.2034John Wiley & Sons, Inc.10.1002/jez.2034http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2034Research Article501510ABSTRACT

Elevation has been proposed as a dominant ecological variable shaping life history traits and subsequently their underlying hormonal mechanisms. In an earlier meta-analysis of tropical birds, elevation was positively related to testosterone levels. Furthermore, parasitism by avian haemosporidians should vary with elevation as environmental conditions affect vector abundance, and while testosterone is needed for breeding, it is hypothesized to be immunosuppressive and thus could exacerbate haemosporidian infection. Our objective in this study was to examine the relationships between elevation, testosterone levels, and parasitism by avian haemosporidians. We surveyed breeding male rufous-collared sparrows (Zonotrichia capensis) across a wide elevational range along the equator. We measured baseline testosterone levels, haemosporidian infection at four elevations spanning the species’ natural range in the Ecuadorian Andes (600, 1500, 2100, 3300 m). Testosterone levels from breeding males were not related to elevation, but there was high intrapopulation variability. Testosterone levels were not related to the probability of parasitism, but our results from one population suggested that the likelihood of being infected by haemosporidian parasites was greater when in breeding condition. In conclusion, even though there is variation in life history strategies among the studied populations, wider divergence in seasonality and life history traits would probably be needed to detect an effect of elevation on testosterone if one exists. Additionally, our results show that variation in testosterone is not related to infection risk of haemosporidians, thus other factors that take a toll on energetic resources, such as reproduction, should be looked at more closely.

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Elevation has been proposed as a dominant ecological variable shaping life history traits and subsequently their underlying hormonal mechanisms. In an earlier meta-analysis of tropical birds, elevation was positively related to testosterone levels. Furthermore, parasitism by avian haemosporidians should vary with elevation as environmental conditions affect vector abundance, and while testosterone is needed for breeding, it is hypothesized to be immunosuppressive and thus could exacerbate haemosporidian infection. Our objective in this study was to examine the relationships between elevation, testosterone levels, and parasitism by avian haemosporidians. We surveyed breeding male rufous-collared sparrows (Zonotrichia capensis) across a wide elevational range along the equator. We measured baseline testosterone levels, haemosporidian infection at four elevations spanning the species’ natural range in the Ecuadorian Andes (600, 1500, 2100, 3300 m). Testosterone levels from breeding males were not related to elevation, but there was high intrapopulation variability. Testosterone levels were not related to the probability of parasitism, but our results from one population suggested that the likelihood of being infected by haemosporidian parasites was greater when in breeding condition. In conclusion, even though there is variation in life history strategies among the studied populations, wider divergence in seasonality and life history traits would probably be needed to detect an effect of elevation on testosterone if one exists. Additionally, our results show that variation in testosterone is not related to infection risk of haemosporidians, thus other factors that take a toll on energetic resources, such as reproduction, should be looked at more closely.
Biochemical Profile, Biological Activities, and Toxic Effects of Proteins in the Rhinella schneideri Parotoid Gland Secretionhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2035Biochemical Profile, Biological Activities, and Toxic Effects of Proteins in the Rhinella schneideri Parotoid Gland SecretionLuis M. Sousa-Filho, Cleverson D. T. Freitas, Marina D. P. Lobo, Ana C. O. Monteiro-Moreira, Renan O. Silva, Lucas A. B. Santana, Ronaldo A. Ribeiro, Marcellus H. L. P. Souza, Gustavo P. Ferreira, Anna C. T. C. Pereira, André L. R. Barbosa, Mauro S. C. S. Lima, Jefferson S. Oliveira2016-08-31T21:25:30.328921-05:00doi:10.1002/jez.2035John Wiley & Sons, Inc.10.1002/jez.2035http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2035Research Article511523ABSTRACT

Parotoid glands of amphibians are known for the production of several biologically active compounds having pharmacological and toxic effects in mammals. In the present work, a protein fraction obtained from Rhinella schneideri parotoid gland (RsPP) was characterized to study its biological and toxic effects. Rhinella schneideri parotoid secretion is composed of up to 30% (w/w) of soluble proteins. Tandem mass spectrometric analysis of the RsPP identified 104 proteins, including actin, beta-actin, ribosomal proteins, catalase, galectin, and uncharacterized proteins; however, no peptidases were found, and this result was reinforced by the absence of proteolytic activity. In addition, RsPP did not exhibit pro-coagulant or antibacterial effects. However, pretreatment of mice with different doses of RsPP intraperitoneally inhibited carrageenan-induced paw edema and increased tissue myeloperoxidase activity. RsPP also reduced interleukin 1β levels in the peritoneal cavities and cell migration in the peritoneal cavities of an animal model of carrageenan-induced peritonitis. Subchronic treatment of animals with RsPP for 7 consecutive days did not alter the serum biochemical, renal, or liver parameters. However, a significant reduction in blood leukocyte count was observed. Our results showed that R. schneideri parotoid secretion contains proteins with anti-inflammatory and slight toxic effects.

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Parotoid glands of amphibians are known for the production of several biologically active compounds having pharmacological and toxic effects in mammals. In the present work, a protein fraction obtained from Rhinella schneideri parotoid gland (RsPP) was characterized to study its biological and toxic effects. Rhinella schneideri parotoid secretion is composed of up to 30% (w/w) of soluble proteins. Tandem mass spectrometric analysis of the RsPP identified 104 proteins, including actin, beta-actin, ribosomal proteins, catalase, galectin, and uncharacterized proteins; however, no peptidases were found, and this result was reinforced by the absence of proteolytic activity. In addition, RsPP did not exhibit pro-coagulant or antibacterial effects. However, pretreatment of mice with different doses of RsPP intraperitoneally inhibited carrageenan-induced paw edema and increased tissue myeloperoxidase activity. RsPP also reduced interleukin 1β levels in the peritoneal cavities and cell migration in the peritoneal cavities of an animal model of carrageenan-induced peritonitis. Subchronic treatment of animals with RsPP for 7 consecutive days did not alter the serum biochemical, renal, or liver parameters. However, a significant reduction in blood leukocyte count was observed. Our results showed that R. schneideri parotoid secretion contains proteins with anti-inflammatory and slight toxic effects.
The Effects of Feeding on Cardiac Control of the Broad-Nosed Caiman (Caiman latirostris): The Role of the Autonomic Nervous System and NANC Factorshttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2036The Effects of Feeding on Cardiac Control of the Broad-Nosed Caiman (Caiman latirostris): The Role of the Autonomic Nervous System and NANC FactorsVictor Hugo Da Silva Braga, Vinicius Araújo Armelin, Mariana Teodoro Teixeira, Augusto Shinya Abe, Francisco Tadeu Rantin, Luiz Henrique Florindo2016-09-21T01:15:24.737419-05:00doi:10.1002/jez.2036John Wiley & Sons, Inc.10.1002/jez.2036http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2036Research Article524531ABSTRACT

The metabolic increment that occurs after feeding demands cardiovascular adjustments to be maintained, as increased heart rate (fH) and cardiac output. In mammals, postprandial tachycardia seems to be triggered by an increase in adrenergic activity and by nonadrenergic noncholinergic (NANC) factors, while in ectothermic vertebrates, this adjustment seems to be linked to a withdrawal of vagal drive as well as to NANC factors. Because the factors behind postprandial tachycardia have not yet been investigated in crocodilians, the present study sought to evaluate the postprandial tachycardia mediators in the broad-nosed caiman. To this end, fasting and digesting animals were instrumented with intraperitoneal cannula and subcutaneous electrocardiogram electrodes (for the measurement of fH, cardiac autonomic tones, and total fH variability, as well as for a power spectral analysis of fH). Data were then collected with the animals in an untreated state, as well as after muscarinic cholinergic blockade with atropine (2.5 mg kg–1) and after double autonomic blockade with atropine and propranolol (5.0 mg kg−1). Fasting animals’ fH was ∼18 bpm, a value which increased to ∼30 bpm during digestion. After the double autonomic blockade, fasting animals exhibited an fH of ∼15 bpm, while digesting animals’ fH was ∼23 bpm. This result is evidence of the presence of NANC factors with positive chronotropic effects acting during digestion. The calculated autonomic tones showed that, after feeding, the adrenergic tone increased while the cholinergic tone remained unchanged. Finally, fH variability analyses revealed that this adrenergic increase is primarily derived from circulating catecholamines.

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The metabolic increment that occurs after feeding demands cardiovascular adjustments to be maintained, as increased heart rate (fH) and cardiac output. In mammals, postprandial tachycardia seems to be triggered by an increase in adrenergic activity and by nonadrenergic noncholinergic (NANC) factors, while in ectothermic vertebrates, this adjustment seems to be linked to a withdrawal of vagal drive as well as to NANC factors. Because the factors behind postprandial tachycardia have not yet been investigated in crocodilians, the present study sought to evaluate the postprandial tachycardia mediators in the broad-nosed caiman. To this end, fasting and digesting animals were instrumented with intraperitoneal cannula and subcutaneous electrocardiogram electrodes (for the measurement of fH, cardiac autonomic tones, and total fH variability, as well as for a power spectral analysis of fH). Data were then collected with the animals in an untreated state, as well as after muscarinic cholinergic blockade with atropine (2.5 mg kg–1) and after double autonomic blockade with atropine and propranolol (5.0 mg kg−1). Fasting animals’ fH was ∼18 bpm, a value which increased to ∼30 bpm during digestion. After the double autonomic blockade, fasting animals exhibited an fH of ∼15 bpm, while digesting animals’ fH was ∼23 bpm. This result is evidence of the presence of NANC factors with positive chronotropic effects acting during digestion. The calculated autonomic tones showed that, after feeding, the adrenergic tone increased while the cholinergic tone remained unchanged. Finally, fH variability analyses revealed that this adrenergic increase is primarily derived from circulating catecholamines.
A Threshold Dosage of Testosterone for Female-to-Male Sex Reversal in Rana rugosa Frogshttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2037A Threshold Dosage of Testosterone for Female-to-Male Sex Reversal in Rana rugosa FrogsAkira Oike, Maho Kodama, Yoriko Nakamura, Masahisa Nakamura2016-09-28T04:51:25.187176-05:00doi:10.1002/jez.2037John Wiley & Sons, Inc.10.1002/jez.2037http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2037Rapid Communication532538ABSTRACT

Androgens play a critical role in testicular differentiation in many species of vertebrates. While female-to-male sex reversal can be induced by testosterone (T) in some species of amphibians, the mechanism still remains largely unknown even at the histological level. In this study, we determined a threshold dosage of T to induce female-to-male sex reversal in the Japanese frog Rana (R.) rugosa. Tadpoles were allowed to metamorphose into frogs with T present in the rearing water. At 0.2 ng/mL T, female frogs formed tissue comprising a mixture of ovary and testis, the so-called ovotestis, the size of which was significantly smaller than the wild-type ovary. Histological changes occurring in the oocytes of T-treated ovaries induced oocyte degeneration in the masculinizing ovaries leading to their final disappearance. In parallel, many germ cells emerged in the cortex of the ovotestis and, later, in the medulla as well. RT-PCR analysis revealed upregulated expression of CYP17 and Dmrt1 but not 17βHSD in the ovotestis, and downregulation of Pat1a expression. Furthermore, immunohistology revealed CYP17-positive signals in the cortex of the masculinizing ovary, spreading throughout the whole area as the testis developed. These results indicate that oocytes are sensitive to T in the ovary of R. rugosa and that male-type germ cells expand in the masculinizing gonad (testis) contemporaneous with oocyte disappearance.

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Androgens play a critical role in testicular differentiation in many species of vertebrates. While female-to-male sex reversal can be induced by testosterone (T) in some species of amphibians, the mechanism still remains largely unknown even at the histological level. In this study, we determined a threshold dosage of T to induce female-to-male sex reversal in the Japanese frog Rana (R.) rugosa. Tadpoles were allowed to metamorphose into frogs with T present in the rearing water. At 0.2 ng/mL T, female frogs formed tissue comprising a mixture of ovary and testis, the so-called ovotestis, the size of which was significantly smaller than the wild-type ovary. Histological changes occurring in the oocytes of T-treated ovaries induced oocyte degeneration in the masculinizing ovaries leading to their final disappearance. In parallel, many germ cells emerged in the cortex of the ovotestis and, later, in the medulla as well. RT-PCR analysis revealed upregulated expression of CYP17 and Dmrt1 but not 17βHSD in the ovotestis, and downregulation of Pat1a expression. Furthermore, immunohistology revealed CYP17-positive signals in the cortex of the masculinizing ovary, spreading throughout the whole area as the testis developed. These results indicate that oocytes are sensitive to T in the ovary of R. rugosa and that male-type germ cells expand in the masculinizing gonad (testis) contemporaneous with oocyte disappearance.
Oxygen Consumption is Limited at an Ecologically Relevant Rearing Temperature in Pupfish Eggshttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2048Oxygen Consumption is Limited at an Ecologically Relevant Rearing Temperature in Pupfish EggsAlexander C. Jones, David Lim, Jacoby J. Wayne-Thompson, Natasha Urbina, Georgina Puentedura, Stanley Hillyard, Frank Van Breukelen2016-10-27T04:26:48.272951-05:00doi:10.1002/jez.2048John Wiley & Sons, Inc.10.1002/jez.2048http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2048Research Article539547ABSTRACT

The habitat of the critically endangered Devils Hole Pupfish, Cyprinodon diabolis is marked by constant high temperatures and low oxygen availability. In order to explore the effects of these conditions on development and recruitment of eggs in Devils Hole, we tested the effects of two ecologically relevant temperatures on the development, hatch success, and oxygen consumption of eggs from a refuge population of pupfish derived from C. diabolis and eggs from its close sister species, Cyprinodon nevadensis mionectes. We developed a simple method to measure oxygen consumption in a single egg. Parent acclimation temperature, rather than incubation temperature, was the most important factor influencing hatch success. Eggs incubated at 33°C hatched more quickly compared to those incubated at 28°C. Despite this accelerated development, larvae from both temperatures were of similar size at hatch. Unexpectedly, eggs incubated at 33°C experience lower than expected oxygen consumption rates compared to those incubated at 28°C. Oxygen consumption rates would be limited at PO2 values that are much higher than environmental oxygen tensions. Oxygen consumption increased dramatically upon hatch, indicating that low oxygen conditions such as those present in Devils Hole may limit developing eggs.

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The habitat of the critically endangered Devils Hole Pupfish, Cyprinodon diabolis is marked by constant high temperatures and low oxygen availability. In order to explore the effects of these conditions on development and recruitment of eggs in Devils Hole, we tested the effects of two ecologically relevant temperatures on the development, hatch success, and oxygen consumption of eggs from a refuge population of pupfish derived from C. diabolis and eggs from its close sister species, Cyprinodon nevadensis mionectes. We developed a simple method to measure oxygen consumption in a single egg. Parent acclimation temperature, rather than incubation temperature, was the most important factor influencing hatch success. Eggs incubated at 33°C hatched more quickly compared to those incubated at 28°C. Despite this accelerated development, larvae from both temperatures were of similar size at hatch. Unexpectedly, eggs incubated at 33°C experience lower than expected oxygen consumption rates compared to those incubated at 28°C. Oxygen consumption rates would be limited at PO2 values that are much higher than environmental oxygen tensions. Oxygen consumption increased dramatically upon hatch, indicating that low oxygen conditions such as those present in Devils Hole may limit developing eggs.
Effects of Water Loss on New Mexico Spadefoot Toad (Spea multiplicata) Development, Spleen Cellularity, and Corticosterone Levelshttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2049Effects of Water Loss on New Mexico Spadefoot Toad (Spea multiplicata) Development, Spleen Cellularity, and Corticosterone LevelsApril L. Bagwill, Matthew B. Lovern, Thomas A. Worthington, Loren M. Smith, Scott T. McMurry2016-10-06T23:51:26.849565-05:00doi:10.1002/jez.2049John Wiley & Sons, Inc.10.1002/jez.2049http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fjez.2049Research Article548561ABSTRACT

Amphibian metamorphosis is complex and larval morphology and physiology are completely restructured during this time. Amphibians that live in unpredictable environments are often exposed to stressors that can directly and indirectly alter physiological systems during development, with subsequent consequences (carryover effects) later in life. In this study, we investigated the effects of water level reduction on development rate, spleen size and cellularity, and examined the role of corticosterone levels in premetamorphic, metamorphic, and postmetamorphic New Mexico spadefoot toads (Spea multiplicata). Based on previous studies, we hypothesized that declining water level would increase tadpole developmental rate, but with the trade-off of increasing corticosterone to a level that would subsequently affect spleen size and cellularity, thus prolonging potential immunological suppression. Declining water levels increased developmental rate by 3 days; however, there were no significant body size effects. Corticosterone (CORT) was negatively correlated with total length, snout vent length, body weight, and spleen weight at metamorphosis, suggesting that size at metamorphosis and the immune system may be affected by excessive CORT levels. When compared to other studies, our results support the view that multiple factors may be acting as stressors in the field affecting amphibian responses, and simple pathways as tested in this study may not adequately represent field conditions.

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Amphibian metamorphosis is complex and larval morphology and physiology are completely restructured during this time. Amphibians that live in unpredictable environments are often exposed to stressors that can directly and indirectly alter physiological systems during development, with subsequent consequences (carryover effects) later in life. In this study, we investigated the effects of water level reduction on development rate, spleen size and cellularity, and examined the role of corticosterone levels in premetamorphic, metamorphic, and postmetamorphic New Mexico spadefoot toads (Spea multiplicata). Based on previous studies, we hypothesized that declining water level would increase tadpole developmental rate, but with the trade-off of increasing corticosterone to a level that would subsequently affect spleen size and cellularity, thus prolonging potential immunological suppression. Declining water levels increased developmental rate by 3 days; however, there were no significant body size effects. Corticosterone (CORT) was negatively correlated with total length, snout vent length, body weight, and spleen weight at metamorphosis, suggesting that size at metamorphosis and the immune system may be affected by excessive CORT levels. When compared to other studies, our results support the view that multiple factors may be acting as stressors in the field affecting amphibian responses, and simple pathways as tested in this study may not adequately represent field conditions.